I thought it was going to be a wonderful day. My high school, Marjory Stoneman Douglas, was full of cheerful students -- many of whom were celebrating Valentine's Day with one another. Even those who didn't have a Valentine seemed like they could find reasons to smile.

As a doctor who works at an international news network, I often see the worst stories of all. In Iraq and Afghanistan, the horrific realities of the battlefield are funneled and concentrated in the medical tents where I have reported for more than a decade. I have seen patients infected with Ebola in West Africa who dehydrate to death, with no treatment in sight. There are other stories I still can't talk about.